On Thu, Sep 30, 2021 at 03:12:45PM +0300, Heikki Krogerus wrote:
> In quirk_huawei_pcie_sva(), use device_create_managed_software_node()
> instead of device_add_properties() to set the "dma-can-stall"
> property.
>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> Acked-by: Zhangfei Gao <zhangfei.gao@xxxxxxxxxx>
> Signed-off-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> ---
> Hi,
>
> The commit message now says what Bjorn requested, except I left out
> the claim that the patch fixes a lifetime issue.
Thanks.
The commit log should help reviewers determine whether the change is
safe and necessary. So far it doesn't have any hints along that line.
Comparing device_add_properties() [1] and
device_create_managed_software_node() [2], the only difference in this
case is that the latter sets "swnode->managed = true". The function
comment says "managed" means the lifetime of the swnode is tied to the
lifetime of dev, hence my question about a lifetime issue.
I can see that one reason for this change is to remove the last caller
of device_add_properties(), so device_add_properties() itself can be
removed. That's a good reason for wanting to do it, and the commit
log could mention it.
But it doesn't help me figure out whether it's safe. For that,
I need to know the effect of setting "managed = true". Obviously
it means *something*, but I don't know what. It looks like the only
test is in software_node_notify():
device_del
device_platform_notify_remove
software_node_notify_remove
sysfs_remove_link(dev_name)
sysfs_remove_link("software_node")
if (swnode->managed) <--
set_secondary_fwnode(dev, NULL)
kobject_put(&swnode->kobj)
device_remove_properties
if (is_software_node())
fwnode_remove_software_node
kobject_put(&swnode->kobj)
set_secondary_fwnode(dev, NULL)
I'm not sure what's going on here; it looks like some redundancy with
multiple calls of kobject_put() and set_secondary_fwnode(). Maybe you
are in the process of removing device_remove_properties() as well as
device_add_properties()?
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/base/property.c?id=v5.14#n533
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/base/swnode.c?id=v5.14#n1083
> There shouldn't be any functional impact.
>
> thanks,
> ---
> drivers/pci/quirks.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index b6b4c803bdc94..fe5eedba47908 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -1850,7 +1850,7 @@ static void quirk_huawei_pcie_sva(struct pci_dev *pdev)
> * can set it directly.
> */
> if (!pdev->dev.of_node &&
> - device_add_properties(&pdev->dev, properties))
> + device_create_managed_software_node(&pdev->dev, properties, NULL))
> pci_warn(pdev, "could not add stall property");
> }
> DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_HUAWEI, 0xa250, quirk_huawei_pcie_sva);
> --
> 2.33.0
>
